Description
Unlike short-term droughts that impact soil moisture levels, streamflows, and surface water supplies more rapidly, long-term droughts develop over several months or years and affect deep water sources like reservoirs and groundwater. They can lead to water restrictions, increased competition for water resources, higher food prices, and economic losses in water-dependent industries. The long-term global Historical Drought Risk product captures risk of drought across the globe using well-established drought monitoring metrics such as Standardized Precipitation and Evaporation Index (SPEI).
Technical Description
The global Historical Drought Risk v2 products capture historical risk of drought across the globe using well-established drought monitoring metrics such as Standardized Precipitation and Evaporation Index (SPEI). This risk indicator was computed using the monthly time series of SPEI at six time scale (6-month, 12-month, 18-month, 24-month, 30-month, and 32-month) and applying the relative frequency approach – the ratio of the number of months when the index is below or equal to a threshold indicating drought of moderate magnitude (SPEI < -1) to the total number of possible outcomes, considering years 1950-2010 as a reference period. These products are categorised into short-term and long-term drought blends for different applications. Short-term products are more suited towards vegetative and agricultural drought monitoring, while the long-term products are more suited towards hydrological drought monitoring.
This dataset contains the following fields:
- drought_frequency: Monthly frequencies of long-term drought occurrence at pixel locations over the baseline time period. This provides frequencies of drought occurrence at pixel locations over the historical baseline period. For instance, a value of 0.5 would indicate that half of the months during the historical period were in long-term drought for that location. These are values between 0.0 and 1.0.
- drought_risk_class: The drought risk classification for each value. Values are integers from 1 to 5 representing the following classes: Very Low Risk (1), Low Risk (2), Moderate Risk (3), High Risk (4), and Very High Risk (5). Values are categorized using the 44th, 67th, 84th, and 94th percentiles of the drought_frequency field, exclusive of '0' values.